Recent studies indicate that several classes of memory deficits in animals are reversible. One facet of the proposed research focuses on determining internal and external conditions which alleviate the memory loss produced by an amnestic treatment (retrograde amnesia) or by maturation of the organism (infantile amnesia). Another aspect of the research is concerned with examining the conditions under which older memory becomes vulnerable to amnestic agents. A major aim involves comparing the nature of amnesia induced for old learning with that induced for newly acquired responses. The proposed experiments will provide information necessary for evaluating the contribution of storage/encoding and retrieval variables as determinants of retention loss.